The invention set forth in this specification relates to the production of silica gel and an adsorbent, absorbent product from sericitic clay.
The term "sericitic clay" used in the title of this specification is intended to indicate a micaceous mineral normally containing a small amount of montmorillonitic type material. Normally, the latter is not a true or traditional montmorillonite because it does not have the expansion characteristics montmorillonite on glycolation. In the particular sericitic clays which are intended to be utilized in connection with the practice of this invention, the sericitic material will normally contain some crystoballite and will also contain a comparatively limited or minor amount of opaline quartz as impurities.
Normally, a sericitic clay of the type indicated in this discussion will contain of from about 40 to about 60% by weight of easily solubilized, amorphous silica. Such silica will either be uncombined or free or will be combined with other oxides so loosely that it can be extracted from the clay by the same methods as can be used in removing uncombined silica. A sericitic clay of the type used with the invention will also normally contain some alumina which is either uncombined or present within compounds which can be so easily broken up so that the alumina present within them can be removed with the same steps as are used to remove free or uncombined alumina. Some of the alumina and the silica will, of course, also be present in the form of zeolitic type compounds which cannot be as easily broken down. Such zeolitic compounds will usually contain various other ingredients such as magnesia, calcium oxide, iron oxides, sodium, lithium and or potassium oxide.
Clays of the type indicated in this discussion can be found in various different locations. In general, all of such clays will have oxide analyses which are substantially similar in character but which will vary slightly from deposit to deposit. Such a typical analysis for a clay of this type mined in the San Joaquin Valley of California in the vicinity of towns such as Taft, McKittrick and others is as follows:
______________________________________ Silica 80.40% Aluminum Oxide 9.48% Iron Oxide 0.88% Calcium Oxide 0.20% Magnesium Oxide 0.54% Sodium & Potassium Oxides 0.15% Loss on ignition (largely 8.35% combined water) 100.00% ______________________________________
Normally, seritic clays of the type indicated in this discussion will not contain greater than 10% more or less by weight of any of the ingredients noted.
Sericitic clays as indicated are in and of themselves comparatively inexpensive and they are commonly utilized for a variety of different, diverse purposes. At present, small chunks or lumps of these clays are utilized as cat litter. Comparatively large amounts of comparatively fine particles are left over from the processing of these clays so as to form such lumps or chunks. Up to the present, such fine particles of sericitic clays have represented an economic waste.
It is considered that such fines cannot be suitably used in many different applications and, as a consequence, they represent an essentially economic waste. A quest for an economic utilization of such fines has resulted in the realization and discovery that they can be processed so as to provide silica gel and an adsorbent, absorbent product believed to have significant utility in various applications such as, for example, in purifying oils, wines and various other liquids. The fact that the invention has been intended to be utilized with "left over" fines of sericitic clay is not to be taken as indicating that the invention cannot be used with clay mined specifically so that it can be processed in accordance with this invention.